The Seismicity of ‘Stable Continental Interiors’

Abstract

In terms of seismic moment or seismic strain release, the deep ocean basins and the ancient cores—the Stable continental interiors'—of the continents are the deadest places on earth. Averaged over the past 200 years, stable continental crust has generated only ~0.3% of the earth's annual seismic moment release. This translates into ~600 plate boundary events of M w ≥ 6.0 for every one that occurs in stable continental crust. Moreover, in the last 200 years the largest earthquakes to occur in the stable interiors or at the passive continental margins have been the 1819 Kutch, India, event and the 1812 (Feb 7) New Madrid, North America, event. With estimated seismic moments in the range of M0 = 0.7–2.5×1028 dyne-cm, these are great earthquakes (M w =7.S-8.2) yet their moments are nearly two orders of magnitude less than those of maximum plate margin events. Virtually all of the largest stable continental earthquakes (M w ≥ 7.0) occur in crust that has been stretched and extended in a rifting process that leads to either failed rifts imbedded in the continents or to passive margin formation, whereas the largest plate margin events occur in convergent tectonic settings. These are just a few of a number of the fundamental seismological differences between stable continental interiors and plate boundaries that are explored and quantified in this paper.